In general, this type of machine comprises a rotary carrousel, equipped with a plurality of supporting plates for the product to be labelled. The carrousel rotates about its own axis so that each product can be brought one after another to a plurality of labelling devices positioned along the edge of the carrousel and each designed to apply one or more labels to the product. Depending on the shape and type of label to be applied, the labelling devices have different structures.
Moreover, to guarantee correct application of each label, the supporting plates are advantageously able to rotate in a controlled fashion about their own axes. An electronic control (usually also known as an “electronic cam”) coordinates the movement of the carrousel, the plates and the labelling devices.
However, to guarantee correct machine operation, depending on the shape and size of the product to be labelled, the labelling devices must be located at predetermined angular positions around the edge of the carrousel. But such positions are not incompatible with labelling products of different shapes and sizes. Depending on the sizes and shapes of the bottles and the labels, the distance between one device and another must be adjusted to allow correct application.
Consequently, this type of labelling machine is not very versatile. Therefore, both the purchase and operating costs are relatively high compared to productivity.
According to the prior art, the most widespread solution for increasing the versatility of machines is to over-equip them in terms of the number of labelling devices, fitting the same machine with two or more identical devices (which apply the same type of label) at two or more different positions along the edge of the carrousel. On each occasion, depending on the type of product to be labelled, only some of the devices are used.
As can immediately be seen, said solution is extremely expensive both because it requires the purchase of two or more identical devices which will only be used alternately, and because it also requires oversizing of the machine as regards the diameter of the carrousel. But larger dimensions imply bigger purchase costs and more space occupied at the company premises.
In most of the machines currently used, the possible positions for the labelling devices along the edge of the carrousel are limited because they correspond to the centres of the sides of a polygonal structure surrounding the carrousel.
Some alternative solutions are described in patents WO 2005/011363, U.S. Pat. No. 4,362,594 and GB 2 138 388 which all allow labelling devices to be mounted at any angular position relative to the carrousel. In said patents, the labelling devices are rigidly fixed to a circular supporting track surrounding the carrousel.
Said solution, although allowing greater positioning variety, also has disadvantages, in particular relative to the need for size change-overs (that is to say, changes in the type of product to be labelled). With each size change-over each labelling device would have to be moved to clearly defined predetermined positions, disconnecting it from the body of the machine. In reality, said operation is very complicated given the weight and size of the labelling devices.